address unchecked return values

(cherry picked from commit ccfd5777)
18 jobs for 702-unchecked-returns-in-server-c-v9_11 in 9 minutes and 9 seconds (queued for 15 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #101462
amd64 docker linux

00:00:17

 
  Build
passed build:centos:centos6:amd64 #101463
amd64 docker linux

00:02:35

passed build:centos:centos7:amd64 #101464
amd64 docker linux

00:02:47

passed build:debian:sid:amd64 #101465
amd64 docker linux

00:01:37

passed build:debian:sid:i386 #101466
i386 docker linux

00:02:03

passed noassert:build:debian:sid:amd64 #101467
amd64 docker linux

00:01:37

 
  Test
passed docs:debian:sid:amd64 #101468
amd64 docker linux

00:00:48

passed install:debian:sid:amd64 #101477
amd64 docker linux

00:03:30

passed noassert:systemtest:debian:sid:amd64 #101479
amd64 docker linux

00:05:38

passed noassert:unittest:debian:sid:amd64 #101478
amd64 docker linux

00:01:14

passed systemtest:centos:centos6:amd64 #101473
linux amd64 docker

00:04:37

passed systemtest:centos:centos7:amd64 #101474
amd64 docker linux

00:05:39

passed systemtest:debian:sid:amd64 #101475
amd64 docker linux

00:05:45

passed systemtest:debian:sid:i386 #101476
i386 docker linux

00:05:59

passed unittest:centos:centos6:amd64 #101469
amd64 docker linux

00:01:12

passed unittest:centos:centos7:amd64 #101470
amd64 docker linux

00:01:20

passed unittest:debian:sid:amd64 #101471
amd64 docker linux

00:01:14

passed unittest:debian:sid:i386 #101472
i386 docker linux

00:01:00